1. Field of the Invention
The present invention relates to a vehicle steering device; and, more particularly, to a vehicle steering device that includes a rotatable steering handle having grips on the left and right sides in a straight-ahead driving position, the steering handle formed to leave a non-grip space (a space in which no grip is provided on the steering handle) on at least one of upper and lower sides thereof, and an airbag provided in the steering handle so that it can be deployed between the steering handle and a driver to restrain the driver in the event of a collision.
2. Description of the Related Art
The steering handle is of a non-circular shape and has no ability to reliably support a rear surface (vehicle's forward side) of the deployed airbag in the non-grip space thereof. Thus, the steering handle cannot effectively support a reaction force generated when restraining the driver with the airbag, making it impossible for the airbag to reliably secure driver restraint performance.
Japanese Patent Application Publication No. 11-342819 (JP-A-11-342819) describes, while taking this into account, a vehicle steering device designed so that an airbag storage casing can be split into upper and lower parts and opened in upward and downward directions during deployment of an airbag, thereby allowing the upwardly and downwardly opened casing to support a rear surface of the deployed airbag in a non-grip space. The casing needs to have an intrinsic strength (rigidity) sufficient to support the rear surface of the deployed airbag.
Because the upwardly and downwardly opened casing can receive (or support) the rear surface of the deployed airbag in the non-grip space, the vehicle steering device described in JP-A-11-342819 is capable of reliably restraining the driver. However, the casing could interfere (or collide) with the driver during its opening process. This is because the casing splits into the upper and lower parts during deployment of the airbag is opened along a trajectory that projects in a vehicle's backward direction from a reference plane including a rotating trajectory of a portion of a steering handle normally facing the driver.